Herbicide Tank Mix Calculator

The whole calculator rests on one identity — your label rate crossed with your carrier rate (GPA) gives the per-gallon concentration, which then scales to your tank and your area.

Branch A (oz/acre):   oz/gal = labelRate ÷ GPA
Branch B (oz/gal):    oz/gal = labelRate                (identity)
Branch C (oz/1000):   oz/acre = labelRate × 43.56
                      oz/gal  = oz/acre ÷ GPA
Branch D (1:X ratio): oz/gal = 128 ÷ (1 + X)

shared (all branches):
  oz to add this tank = oz/gal × tankGal
  water / carrier gal = tankGal − (oz to add ÷ 128)

coverage (per-area branches):
  acres this tank covers = tankGal ÷ GPA
  tanks needed           = ceil(area acres ÷ acres-per-tank)   (round UP)

Worked example: a 32 oz/acre label, a sprayer calibrated to 20 GPA, and a 100-gal tank → 32 ÷ 20 = 1.60 oz/gal × 100 gal = 160 fl oz of concentrate, covering 100 ÷ 20 = 5.00 acres, with about 98.75 gal of water.

The 43.56 constant is 43,560 sq ft per acre ÷ 1,000. The 128 constant is fluid ounces per US gallon. The GPA field is your sprayer's calibration — it is not printed on the label; the 1/128th method (catch one nozzle's output over a 340 sq ft plot — the ounces caught ≈ GPA) is the quickest way to find it. Tanks needed always rounds up: rounding down leaves coverage short.

Sources: Ohio State Extension FABE-530 (calibration & sprayer math; acres-per-tank method), Tennessee PSEP (common pesticide calculations), and Pesticide Environmental Stewardship (the 1/128th ounces-to-gallons method). Secondary cups / tbsp / mL measures are display helpers (1 cup = 8 fl oz, 1 tbsp = 0.5 fl oz, 1 fl oz = 29.5735 mL).

Getting the mix right is the first half of the job; knowing what it costs is the second. Jug price converted to a cost per 1,000 square feet prices the same tank you just built, and what a season of treatments should bill carries that material cost into the price of the round. The GPA figure everything above depends on comes off a measured sprayer calibration, never off the label. This page is the pre-mix dosing half of the visit; the pesticide application log worksheet is the record you fill in afterwards.